A hemophilia drug sharply cuts the chances that victims of the most devastating type of stroke will die or be severely disabled, providing the first possible treatment for brain hemorrhages, researchers reported Saturday.

An international study involving 400 patients found that a single infusion of the drug, a synthetic version of a naturally occurring protein, given within three hours after onset cut by about one-third the risk of death or severe disability among patients in the midst of a bleeding stroke. This type of stroke hits about 80,000 Americans each year and about 2 million people worldwide.

The findings mark only the second time that any treatment has been shown to be effective for any type of stroke and the first time a treatment has been found effective for bleeding strokes, which are the deadliest and most disabling.

"These results are beyond my wildest dreams," said Stephan Mayer, an associate professor of neurology and neurosurgery at Columbia University Medical Center in New York, who led the study. "I thought this might work, but I had no idea it would work so well. I'm walking around in a state of shock. I'm very excited."

Although the drug, NovoSeven, probably requires additional testing before winning formal approval for use with stroke patients, Mayer and other experts predicted it would likely become the standard treatment and transform care for what had essentially been tens of thousands of hopeless patients.

"The results we've seen are just so eye-popping that I have no doubt that eventually this is going to become the standard treatment for stroke around the world," said Mayer, who unveiled his findings at the World Stroke Congress in Vancouver. "The results are so clear, so consistent and so robust it is truly remarkable."

Other experts welcomed the findings.

"This is very significant. It's something that we've been looking for and hoping for and waiting for," said Larry Goldstein, director of the stroke center at the Duke University Medical Center, who also serves as a spokesman for the American Stroke Assn.